The basic objective of the proposed research is to obtain a clearer knowledge of the cellular mechanisms involved in retinal degenerations caused by light exposure in the albino rat and by inherited retinal disease in the Royal College of Surgeons (RCS) strain of rat. These two cases have been proposed as animal models for the human degenerative disease, retinitis pigmentosa. Thus, a related objective is to more firmly establish the resemblance of these two animal models to retinitis pigmentosa. The focus of the proposed work will be to probe the degenerating visual mechanisms as they contribute to threshold and receptive field properties, light adaptation, dark adaptation and spectral sensitivity by using single unit recordings from the optic tract and lateral geniculate nucleus and by recording electroretinograms and the early receptor potential. An attempt will be made to assess higher visual pathway function independent of retinal function by recording responses of lateral geniculate nucleus cells to electrical stimulation of the optic nerve. The linkage between retina and lateral geniculate nucleus will be probed by dual recording from the retina and lateral geniculate nucleus. In addition to this physiological assay, behavioral testing for visual capacity will be done.